if i recall correctly (not at my daw now), you can monitor everything in and out of the delta 66 when you're speakers are hooked up to outputs 1/2 and you set their output (in the control panel) to "monitor/mix" or something like that.
acid may have an option in the record window to monitor input too (or perhaps in the preferences menu?), and i think you'll want to keep your inputs for recording set to the hardware inputs you're connected to, not the monitor/mix.
try to run in asio mode to keep latency down (in acid's audio preferences window). oh, and make sure all the virtual faders are up in the delta's control panel, and that nothing is muted or soloed.
good luck,
marcus